Submitted by Prerak Juthani

Let's say you were trying to get a bacterium to produce protein. At the beginning of which of the following phases mentioned above should you induce the production? a) Lag phaseb) Log Phase c) Stationary phased) Decline phasee) None of the above

The correct answer is...

B, log phase. The reason for this is because you want to attain the most protein possible, and the time during which the bacterium is likely to be making protein is when it is consistently dividing. In the lab, you can tell that you are at the start of the log phase when you take your bacterial cell sample and measure its absorbance at 600 nm (usually at the start of the log phase, you have an Optical Density (OD) of about .6 (for E. Coli at least). The bacterium is unlikely to be making protein in the lag phase because, at that point, it is examining its external environment, while its internal environment stays constant. Similarly, in the stationary phase, the cell is unlikely to be doing anything (decreased transcription and translation) because it has stopped dividing. And in the death phase, the bacteria are actually dying, so that would also not help.